Solution: The following line of code will set the Web Page Security Validation expiry to 60 minutes

SPWebApplication webApp = SPWebApplication.Lookup(new Uri("http://webappURL/")); //Use TimeSpan constructor to specify Days, hours, minutes, seconds webApp.FormDigestSettings.Timeout = new TimeSpan(1, 0, 0); //Save the changes webApp.Update();Note: You'll get access denied error when the above code is executed within RWEP as it runs the code under the Application Pool account of the your web application. You need to run this code with farm account as the SPWebApplication is stored in config database. Use SPUserToken and farm account to run this code.